ELECTRON-MOBILITY AND SI INCORPORATION IN INXGA1-XAS LAYERS GROWN ON GAAS BY MOLECULAR-BEAM EPITAXY

Layers of InxGal-xAs with In-mole fraction ranging from 0 to 1 were grown on GaAs by molecular beam epitaxy. The electron mobility was measured by Hall effect as a function of both In concentration and temperature. The mobility was found to depend strongly on the composition. These experimental results were accurately calculated based on scattering from ionized impurities, polar optical phonons, the disordered alloy, and dislocations. In addition, the effect of space charge scattering is discussed. For layers with 0.2 less-than-or-equal-to x less-than-or-equal-to 0.85 the mobility monotonically declined with reduced temperature below 300 K as an effect of increased ionized impurity and space charge scattering. Free-carrier concentration due to Si-doping of InAs layers was also investigated. This was found to vary exponentially from the 10(16) to 10(19) cm-3 with the inverse Si-source temperature. The highest measured value was 3.3 X 10(19) cm-3 and the carrier concentration saturated above this. For such high values the surface was deteriorated which we attributed to precipitation of silicon.